1. Field of the Invention
The present Invention relates to a method and apparatus for the control of a subscriber identity module in a data communication system, preferably a mobile telephone network.
2. Description of the Background Art
In a mobile communication system, system subscriber data are stored in a unit or device specially designed for data management. For instance, in a GSM system such a device is the home location register (HLR). Stored in the HLR are certain parameters related to the subscriber or subscription, such as the mobile subscriber international ISDN number (MSISDN) and the international mobile subscriber identification (IMSI) code.
In practice, the capacity of a single physical home location register is limited. For example, the home location register devices used in GSM systems can typically handle about 200,000 to 300,000 customers. Therefore, large operators require at least several home location register devices.
The data contained in the subscriber identity module that is used in a mobile communication system includes the same data that are stored in the home location register. In addition to that data, the subscriber identity module contains a secret key Ki used for encryption of wireless or radio communications and for authentication of the mobile station. The data are generally added at the last stage of production of the subscriber identity module in conjunction with its personalization. After such personalization, changing that data is either very difficult or impossible.
Nevertheless, the customer may lose his/her subscriber identity module, or the module may be damaged. Therefore, the operator must store subscriber identity modules suited for all home location registers at each customer service point if the operator wishes to provide flexible and full service operations for the renewal, reconstitution and control of subscriber identity modules. If the operator has, by way of example, 20 home location registers in its mobile communication system, then the customer service points must have an assortment of 20 subscriber identity modules containing different data This gives rise to a distinct logistical problem as well as problems of efficiency concerning invested capital in the maintained subscriber identity modules.